Riveter or the like having a pressure multiplying device



July 15, 1952 R. NlsslM RIVETER 0R THE LIKE HAVING A PRESSURE MULTIPLYING `DEVICE l Filed Eug. zo, 1947 NVENTOR 'Wwf /Zm ATTORNEY atented July l5, 1952 ARaoul Nissim, London, England, assigncrvtp Resista-nceWelders Limited, lnvernesaslcotland Application August 20, 1947, SerialjNolg'769,571v

In Great Britain October 5, 1943 Y Section 1, Public Law 690,'ugust" 8,1946 u Patent expires October 5, 1963 The present invention relates 'to a fluid-operated device for multiplying pressure, and may be used to operate any form of tool requiring the useof a high pressure, .such as a riveting tool operating either by squeezing a solid rivet or by pulling an oversize mandrel througha hollow rivet.Y Y y f The operation of such devices off a compressed air supply is already common practice, and as the pressure (80 to 100 lbs. per square inch) at which compressed air is usually supplied is too low to operate the devices directly oif the air supply line, some form of pressure multiplier is interposed between the air supply and the tool to give a pressure of perhaps 6000 lbs. per square inch. Thus, for example, it is known to use air pressure to move the differential piston of a hydraulic piston and cylinder of comparatively large diameter and stroke; the air pressure applied to the larger face of the differential piston being transferred to liquid on the smaller face with a multiplication factor equal to the ratio of the areas of the two faces. The pressure developed in the liquid in this manner is then transferred, via a flexible pipe, to the tool effecting the riveting or other operation.

A differential piston and cylinder used in this way constitutes a form of pressure multiplier, but although multiplication adequate for most purposes can be achieved in this manner, the tool suffers from certain disadvantages. Thus, in order to give the required pressure multiplication and the required work, the differential piston must be of comparatively large cross-section and have a fairly large travel; consequently owing to its weight and bulk, it cannot be incorporated in the hand tool, but must be mounted separately and connected to the tool by a flexible pipe capable of withstanding the fully multiplied pressure. Another disadvantage arises out of the fact that in the operation of squeeze riveters, for example, the squeezing members have to be moved apart, for convenience of handling, a distance greater than that required for the actual riveting. In the known apparatus described the fully multiplied pressure is used to move the squeeze members apart and/or bring them together up to the riveting position, whereas both of these movements could be performed with the employment of far less power.

It is an object of the present invention to provide a tool which is easy and cheap to manufacture, is of small bulk and weight, is easily and exibly handled, which does not require the use of very high pressure hose between the multiplier and the tool, and in which the fully In 'order that; the nature of the, invention",v may lbe more'clearlyappreciatedla preferred example will nowlbe described with reference to the ac ccmpanying diagrammatic drawing yof a riveting .tool in whichftheiigure illustrates@J simple :tool in which the whole of themultiplication offp'ressure required for the power stroke is achieved in the tool itself.

Referring to the drawing, a pressure-applyin tool comprises a casing 9 to which is attached a pipe Iii through which, from a supply reservoir II, compressed air at a comparatively low pressure is supplied to a chamber I2. Pressure of the fluid causes downward movement of a diiferential piston I3 against the resistance of a spring Ill thereby compressing a fluid, such as oil, contained in a chamber I5. A second piston I6 is held from downward movement by a spring I1 until pressure in the chamber I has attained a predetermined level sufficient to overcome the action of the spring.

As the differential piston I3 moves downwardly the duid contained in the chamber I5 is forced through a port I8 into a passage IS in a stem 2B of the piston I6 and thence into a chamber 2I. The pressure of the fluid acts on a piston 22 of a ram 23 to make what will be called the approach stroke of the ram. It will be noted that this approach stroke is made with fluid at arcomparatively low pressure which is not multiplied, but as this pressure acts on the large face of the dierential piston I3 to displace the oil and therefore the smaller piston 22, the ram 23 moves a greater distance than the piston I3. A return spring 24 is slightly compressed during the approach stroke.

When the approach stroke has been completed and the ram 23 bears against the work which is not shown but is located between the ram 23 and an anvil 25 the differential piston I3 is still acted upon by the compressed air entering by the pipe I0 and the fluid pressure in the chamber I5 will therefore increase until the predetermined level is reached when the piston'l is displaced against the action of spring Il, air in chamber 26 escaping through ports 21.

When a valve 28 formed integrally with the piston I3 abuts against a valve seating 29 on the stem 20, port I8 is closed and the members I3 and 20 thereafter move as a single unit and act as a single differential piston giving a multiplication of specific pressure. Continued movement of the differential piston I3 displaces the uid in the passage IS and chamber 2| to cause the power stroke of the ram 23. It will be appreciated that the specific pressure or pressure per unit area, applied to the piston 22 is equal to the specific pressure applied to the piston I3 multiplied by a factor equal to the ratio of the cross-sectional areas of pistons I3 and 22 respectively.

The uid pressure applied through the pipe I0 may be cut oi by valve IIA and the chamber I2 opened to atmosphere, the springs I4, I1, '24 and 30 then causing the several `parts and the iiuid to return to their initial positions.l

The low pressure supply may be that given by compressed air, steam or gas or other corri pressible uid whilst the fluid operating against the ram may be incompressible such as water or oil. Y

I cla-im: Y

A pressure applying tool including a first' cylinfder, a. rst piston in said cylinder operated by fluid pressure to effect a power stroke, a liquid storage chamber bounded on opposite sides respectively by said piston and by a .resiliently loaded movable wall. a second cylinder smaller than the first, a second piston in said second cylinder, a passage in said second piston connecting the storage chamber to the second cylinder, a ram actuated by the pressure of liquid 4 in said second cylinder, cooperating means on said first piston and said second piston for closing said passage after a predetermined relative movement of said pistons, and resilient means acting on said second piston to resist its movement, whereby fluid pressure acting on Ythe rst piston rst displaces said piston relative to the second piston to displace liquid from the storage chamber into the second cylinder until the completion of the predetermined relative movement, after which the passage is closed, and the second piston moved mechanically by the first piston to apply pressure to the liquid in the second cylinder.

RAOUL NISSIM.

FERENCES CITED The following references are of record in the le of this patent: 

